The official gazette of Japanese Patent Public Disclosure (KOKAI) No. Hei 3-95177 discloses 1-cyclopropyl-6-fluoro-1,4-dihydro-8-methoxy-7-(3-methylaminopiperidin-1-y l)-4-oxoquinoline-3-carboxylic acid (hereunder designated "Q-35"). The official gazette further teaches that Q-35 is the product of recrystallization from acetonitrile and that it has satisfactory antimicrobial activity.
However, as continued research was undertaken to commercialize it as a medicine, the Q-35 recrystallized from acetonitrile turned out to have only low stability due to the drawback that its weight would increase with increasing humidity. Under the circumstances, it was impossible to administer the Q-35 in well-defined doses and this, combined with other problems of the Q-35 made it difficult to develop said compound as a medicine. Hence, there was the need to develop a technique by which stable Q-35 could be produced even under humid conditions.